Pulse transit time based on piezoelectric technique at the radial artery

Pulse transit time (PTT) has shown its potential in relevant cardiovascular and cardiorespiratory studies. However, the use of photoplethysmography (PPG) in PTT measurement can be limited in events of poor peripheral perfusion. Uninterrupted PTT monitoring may also not be achievable when less cooperative patients distribute the PPG probe due to its prominent light source. Hence, there is a need for an alternative method to measure PTT in such incidents. In this study, the piezoelectric (PIEZO) technique to detect pulsations from a human wrist above the radial artery to estimate PTT is presented. 17 healthy adults (11 male; age range of 21-33 years) were recruited to compare PTT and heart rate (HR) differences between the PPG and PIEZO methods. These time-related derivations were made with respect to an electrocardiogram (ECG). The timing consistency of the PIEZO transducer shows significant correlations (p < 0.01) to those derived from the ECG and a pulse oximeter. Particularly, there is a high level of agreement of < 1 beat per minute (bpm) difference in HR estimates observed when compared to the two commercial devices in the respective Bland-Altman plots. Comparison of PTT obtained from the PIEZO transducer against the PPG signal shows constantly lower values due to the shorter path length it requires to propagate. A regression equation was formulated to relate the PTT values acquired from both these signals. Preliminary findings herein suggest that the PIEZO technique can be useful as an alternative for PTT monitoring. This shows promise to be more accommodating for less cooperative patients or those with insufficient peripheral perfusion.